The proposed research is intended to further develop the multiple-channel theory for spatial vision. One form of this theory postulates a Fourier-like analysis by multiple, narrowly-tuned channels on the spatial attributes of a visual stimulus. Recent research, however, suggests that the visual system also contains channels capable of responding to a relatively broad band of spatial frequencies. Furthermore, there is evidence that at least some of these are phase-selective in their responses. A pulsed simultaneous masker paradigm will be used to examine some of the characteristics of broad-band channels. An attempt will be made to catalogue at least a few of the types of broad-band phase-selective channels and the range of stimulus contrasts over which they operate. Once some of the broad-band channel parameters are better understood, an attempt will be made to elucidate the nature of the relationship broad-and narrow-band channels. For example, an investigation could be conducted to determine if broad- and narrow-band channels process spatial information in parallel or in series. BIBLIOGRAPHIC REFERENCES: Sansbury, R.V. (1977) Contrast increment detection of the square-wave third harmonic: some support for the hypothesis of independent spatial-frequency channels. Vision Res. 17.